Shani refers to him in quite a good number of the conversations Geralt has with her. She even mentions his death to Geralt. He is also mentioned, not by name, by one of the nurses at St. Lebioda's Hospital. Both she and Shani quote Rusty as saying "Stitch red to red and white to white and everything will be alright".
In the Enhanced Edition of the game, this little mantra was augmented to "Stitch red to red, grey to grey and white to white and everything will be alright".
He is the author of a book entitled "The Rudiments of Pathomorphology".
His mantra seems to be quoted again (seemingly by reading it from somewhere) in the third installment of the game during the mission Contract: Oxenfurt Drunk by the medic that gives Geralt access to the morgue after giving him the key. On this case his saying was altered a bit once again.
" 'Stitch red to red, yellow to yellow, and white to white'... Very funny..."
There is also a gwent card that bears that description.